Low power, inexpensive velocity detection using a pir array

ABSTRACT

Methods and systems may include a system including a first passive motion sensor having a lateral field of view with a first edge and a second passive motion sensor having a lateral field of view with a second edge that is substantially parallel to the first edge. The first and second edges can define a virtual beam. The system may also include logic to receive signals from the first and second passive motion sensors and determine a gait velocity and level of activity based on the signals from the first and second passive motion sensors.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to and claims the benefit under 35 U.S.C. 120 of U.S. application Ser. No. 12/984,713, filed on Jan. 5, 2011, which will issue as U.S. Pat. No. 8,772,724 on Jul. 8, 2014, the entire contents of which is incorporated herein by reference.

BACKGROUND

1. Technical Field

Embodiments generally relate to motion sensing. More particularly, embodiments relate to the use of virtual sensing beams to determine spatial gait parameters in a passive motion sensing environment.

2. Discussion

Existing techniques for measuring the velocity of a human in a home can be inaccurate, expensive, power inefficient, damaging to the installation structure, and potentially hazardous. For example, active solutions such as infrared beam-based systems can be power inefficient. Other solutions might involve wearable devices, but the devices must be remembered by the individual in question. Additionally, floor sensors may require carpet modification or the addition of a relatively expensive pressure floor mat that could pose a trip hazard.

Solutions that use a passive infrared (PIR) sensor may be more power efficient than active solutions, but can suffer from inherent limitations of PIR sensor accuracy. For example, existing PIR sensor devices might sense motion in a single downward facing wedge shaped three-dimensional space, which, due to its spread over distance, can make velocity measurements uncertain. Furthermore, because PIR sensors may not be as accurate when approached at angles non-orthogonal to the edge of the sensing edge, a walker moving down a hallway could trigger the PIR sensor under an imprecise geometry. Simply put, there remains considerable room for improvement with regard to motion sensing and gait analysis.

BRIEF DESCRIPTION OF THE DRAWINGS

The various advantages of the embodiments of the present invention will become apparent to one skilled in the art by reading the following specification and appended claims, and by referencing the following drawings, in which:

FIGS. 1A and 1B are top views of examples of sensor arrays having a substantially two-dimensional virtual sensing beam according to an embodiment;

FIG. 2 is a side view of an example of a sensor array having a substantially two-dimensional virtual sensing beam according to an embodiment;

FIG. 3 is a front view of an example of a sensor array having a substantially one-dimensional virtual sensing beam according to an embodiment;

FIG. 4 is a top view of an example of a system having a pair of sensor arrays according to an embodiment;

FIG. 5 is a top view of an example of a system having four sensor arrays according to an embodiment;

FIG. 6 is a signal diagram of an example of a set of signals from a plurality of sensor arrays according to an embodiment;

FIG. 7 is a signal diagram of an example of a set of signals from a sensor array according to an embodiment;

FIG. 8 is a flowchart of an example of a method of determining gait velocity and level of activity according to an embodiment; and

FIG. 9 is a block diagram of an example of a system according to an embodiment.

DETAILED DESCRIPTION

Embodiments may involve a method in which signals are received from a first passive motion sensor and a second passive motion sensor, wherein the first passive motion sensor has a lateral field of view with a first edge. The second passive motion sensor can have a lateral field of view with a second edge that is substantially parallel to the first edge so that the first and second edges define a virtual beam. The method may also involve determining a gait velocity based on signals from the first and second passive motion sensors.

Embodiments can also provide for an apparatus including a first passive motion sensor having a lateral field of view with a first edge, and a second passive motion sensor having a lateral field of view with a second edge that is substantially parallel to the first edge. The first and second edges may define a first virtual beam.

Other embodiments may provide for a system including a first passive motion sensor having a lateral field of view with a first edge, and a second passive motion sensor having a lateral field of view with a second edge that is substantially parallel to the first edge. The first and second edges may define a first virtual beam. The system can further include logic to receive signals from the first and second passive motion sensors, and determine a gait velocity based on the signals from the first and second passive motion sensors.

FIG. 1A shows a passive infrared (PIR) sensor array 10 having a plurality of PIR sensors 12 (12 a, 12 b) installed in a hallway environment. Generally, each PIR sensor 12 is passive in that it does not emit energy and can detect the movement of nearby individuals by reading relative energy (e.g., heat) changes in the field of view of the sensor 12. In particular, a first PIR sensor 12 a has a lateral (e.g., side-to-side) field of view defined by a rightmost edge 14 and a leftmost edge 16. Similarly, a second PIR sensor 12 b has a lateral field of view defined by a rightmost edge 18 and a leftmost edge 20. In the illustrated example, each sensor 12 is mounted at an angle 8 so that its field of view is generally tilted to the left. As a result, the rightmost edge 14 of the first PIR sensor 12 a and the rightmost edge 18 of the second PIR sensor 12 b are substantially parallel to one another and define a uniform virtual beam 22 that can be tightly controlled to detect motion in a relatively small sensing area. Accordingly, activity in areas falling outside the virtual beam 22 such as area 24 or area 26 (if the illustrated door is left open) can be eliminated from consideration by the PIR sensor array 10. Moreover, because a direction 28 of expected travel down the hallway (e.g., the longitudinal axis of the hallway) is substantially perpendicular to the virtual beam 22, the reliability and certainty of the PIR sensor array 10 can be substantially increased. The illustrated PR sensor array 10 is also equipped with a leveling indicator 11 to facilitate in the installation of the PIR sensor array 10 against a wall 13. Thus, the leveling indicator 11 may be particularly advantageous in environments in which the wall 13 has a tilt of its own.

FIG. 1B demonstrates that a virtual beam 23 might also be obtained by tilting the PIR sensors 12 to the left. As a result, the virtual beam 23 in the illustrated example is formed from the leftmost edge of the first PIR sensor 12 a and the leftmost edge 20 of the second PR sensor 12 b. Moreover, the PIR sensors 12 need not be tilted in the same direction (i.e., one could be tilted to the left and the other to the right, or vice versa). Additionally, the PR sensors 12 could be tilted up or down as appropriate.

Turning now to FIG. 2, a side view is shown in which a sensor array 30 is mounted to the wall of a hallway. The illustrated sensor array 30 includes a pair of horizontally positioned passive motion sensors 32 (32 a, 32 b) having lateral fields of view with edges 35, 37 that provide a substantially two-dimensional (e.g., planar) vertical virtual beam with a footprint 34 on an opposing wall 36. In the illustrated example, the rightmost edge 35 of the field of view of a first passive motion sensor 32 a and the rightmost edge 37 of the field of view of a second passive motion sensor 32 b produce the virtual beam. Although the illustrated fields of view are conical in shape, other shapes such as pyramids might also be provided by the passive motion sensors 32.

FIG. 3 shows a front view of a sensor array 38 having three passive motion sensors 40 (40 a-40 c). In the illustrated example, a first passive motion sensor 40 a has a field of view that projects to a perimeter 42, which is skewed upward and to the side due to an intentional tilt angle of the first passive motion sensor 40 a. A second passive motion sensor 40 b is disposed beside (i.e., horizontal to) the first passive motion sensor 40 a and has a field of view that projects to a perimeter 44. Similarly, a third passive motion sensor 40 c can project to a perimeter 46, wherein the third passive motion sensor 40 c may be disposed beneath (e.g., vertical to) the first and second passive motion sensors 40 a, 40 b. The edges of the perimeters 42, 44, 46 can be positioned to overlap and define a lateral virtual beam 50 that is substantially one-dimensional (e.g., the longitudinal dimension is much greater than the other two dimensions). The illustrated approach can be particularly useful in an environment with pets because the lateral virtual beam 50 can be placed at a height to detect only humans (e.g., average shoulder height). In the illustrated example, when all four passive motion sensors are triggered, it can be determined that an individual is within the lateral virtual beam 50.

Turning now to FIG. 4, another approach is shown in which a plurality of sensor arrays 52, 54 are used to partition an area into a plurality of zones (i.e., zones “A” through “K”). In the illustrated example, the passive motion sensors of a first sensor array (“PIR Array Y”) 52 are angled to the right and have fields of view edges that define a first virtual beam 56 and a second virtual beam 58, and the passive motion sensors of a second sensor array (“PIR Array Z”) 54 are angled to the left and have fields of view edges that define a third virtual beam 60 and a fourth virtual beam 62.

With continuing reference to FIGS. 4 and 6, example output signals from the passive motion sensors of the first and second sensor arrays 52, 54 are shown for a scenario in which an individual walks along a path 68 though the partitioned area. In general, the output signals transition to a high value (i.e., exhibit a rising edge transition) when motion is detected by the corresponding passive motion sensor and remain high until motion is no longer detected. Additionally, a lack of detected motion can cause the output signals to transition to a low value (i.e., exhibit a falling edge transition). Alternative signaling schemes such as an inverted scheme in which a rising edge transition corresponds to a lack of detected motion and a falling edge transition corresponds to detected motion, or a level based scheme in which one voltage level corresponds to detected motion and another voltage level corresponds to a lack of detected motion, might also be used.

In the illustrated example, a first output signal 70 from a first passive motion sensor (“S1”) 64 contains a rising edge transition that indicates entry of the individual into zone “J” and begins time period Δt₁ When a second output signal 72 from a second passive motion sensor (“S2”) 66 exhibits a rising edge transition it can be determined that the individual has entered zone “H” corresponding to time period Δt₂. A falling edge transition in the first output signal 70 can indicate that the individual has left the field of view of the first passive motion sensor 64 and entered zone “F”, which corresponds to time period Δt₃. When the second output signal 72 exhibits a falling edge transition, it can be determined that the individual has entered zone “E” associated with time period Δt₄. Similarly, third and fourth output signals 74, 76 from third and fourth passive motion sensors 78, 80, respectively, can be used to detect the individual's passage through zones “C” (corresponding to time period Δt₅), “D” (corresponding to time period Δt₆), and “A” (corresponding to time period Δt₇).

In addition to detecting the presence of the individual in the various zones, the illustrated approach enables detection of staggering walking patterns. For example, if the path 68 is not straight, movement might be detected in other zones such as zone “I” or “B”. Moreover, the illustrated approach enables determinations of gait velocity to be made. For example, because the width (e.g., distance between edges) of the first virtual beam 56 is known, the time period Δt₁ can be used to determine the gait velocity of the individual while in zone “J”, wherein the gait velocity is the beam width divided by the time period Δt₁. Similar gait velocities can be calculated for movement through each of the other virtual beams, and the individual gait velocities might be averaged together on a weighted or non-weighted basis as appropriate. Additionally, a gait velocity calculation can be made for the time period Δt₀ between the initial rising edge transitions for the first passive motion sensor 64 and the fourth passive motion sensor 80 (e.g., across multiple arrays).

With continuing reference to FIGS. 4 and 7, a set of output signals is shown in which an individual stops within a zone of the partitioned area and turns around. In the illustrated example, an output signal 82 of the first passive motion sensor 64 contains a rising edge transition that indicates entry of the individual into zone “J” and begins time period Δt₈. When a second output signal 84 from the second passive motion sensor 66 exhibits a rising edge transition it can be determined that the individual has entered zone “H” corresponding to time period Δt₉. A concurrent falling edge transition in both output signals 82, 84 can indicate that the individual has stopped moving within zone “H”, corresponding to time period Δt₁₀. The falling edge transitions need not be exactly concurrent so long as the time difference between the two transitions would not reasonably be attributable to the individual passing through a virtual beam (e.g., concurrence can be dependent upon a velocity threshold being exceeded).

In the illustrated example, a concurrent rising edge transition in both output signals 82, 84 may indicate that the individual has started moving again in zone “H”, corresponding to time period Δt_(n). The individual's reentry to zone “J” can be detected based on a falling edge transition in the output signal 84 of the second passive motion sensor 66 while the output signal 82 of the first passive motion sensor 64 remains high, wherein time period Δt₁₂ corresponds to such reentry. The individual's exit from the monitored area may be indicated by the final illustrated falling edge transition in the output signal 82.

FIG. 5 demonstrates that a monitored area may be partitioned into an even larger number of zones. In the illustrated example, additional sensor arrays such as sensor array (“PIR Array W”) 86 and sensor array (“PIR Array X”) 88 might be positioned on different walls to generate virtual beams in other directions and at other angles. Such an approach could be particularly advantageous in a larger area such as a living room or bedroom.

Turning now to FIG. 8, a method 90 of determining gait velocity and level of activity is shown. The method 90 may be implemented in executable software as a set of logic instructions stored in a machine- or computer-readable medium of a memory such as random access memory (RAM), read only memory (ROM), programmable ROM (PROM), firmware, flash memory, etc., in fixed-functionality hardware logic using circuit technology such as application specific integrated circuit (ASIC), complementary metal oxide semiconductor (CMOS) or transistor-transistor logic (TTL) technology, or any combination thereof. For example, computer program code to carry out operations shown in method 90 may be written in any combination of one or more programming languages, including assembly language programming, an object oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the “C” programming language or similar programming languages.

Processing block 92 provides for receiving output signals from one or more passive motion sensor arrays. As already noted, the sensor arrays may include passive motion sensors that are angled so that the sensor arrays have lateral field of view edges that define one or more virtual beams. Thus, the output signals can indicate the order of activation/triggering of the passive motion sensors as well as the time differences between triggering events (e.g., time periods Δt₁-Δt_(n), as already discussed). A gait velocity determination can be made at block 94 based on the received signals and one or more distances between virtual beam edges. In one example, the distances between virtual beam edges are predetermined and stored to a memory location, wherein block 94 might include retrieving the distances from the memory location. In addition, levels of activity in area zones can be determined at block 96 based on the received signals and/or the distances between virtual beam edges. For example, if the monitored area is a household kitchen partitioned into multiple zones, the determination at block 96 might involve determining the amount of time the individual has spent washing dishes at the sink versus sitting at the kitchen table. Illustrated block 98 provides for outputting the determined gait velocities and levels of activity.

FIG. 9 shows a system 100 having one or more PIR arrays 102, a processor 104, system memory 106, an input/output hub (IOH) 108, a network controller 110, and various other controllers 112. Portions of the system 100 could be part of a mobile platform such as a laptop, personal digital assistant (PDA), mobile Internet device (MID), wireless smart phone, media player, imaging device, etc., or any combination thereof. In addition, the system 100 may also be part of a fixed platform such as a personal computer (PC), server, workstation, etc. Thus, the processor 104 may include one or more processor cores 114 capable of executing a set of stored logic instructions, and an integrated memory controller (IMC) 116 configured to communicate with the system memory 106. The system memory 106 could include dynamic random access memory (DRAM) configured as a memory module such as a dual inline memory module (DIMM), a small outline DIMM (SODIMM), etc.

The illustrated IOH 108, sometimes referred to as a Southbridge of a chipset, functions as a host device and communicates with the network controller 110, which could provide off-platform communication functionality for a wide variety of purposes such as cellular telephone (e.g., W-CDMA (UMTS), CDMA2000 (IS-856/IS-2000), etc.), WiFi (e.g., IEEE 802.11, 1999 Edition, LAN/MAN Wireless LANS), Low-Rate Wireless PAN (e.g., IEEE 802.15.4-2006, LR-WPAN), Bluetooth (e.g., IEEE 802.15.1-2005, Wireless Personal Area Networks), WiMax (e.g., IEEE 802.16-2004, LAN/MAN Broadband Wireless LANS), Global Positioning System (GPS), spread spectrum (e.g., 900 MHz), and other radio frequency (RF) telephony purposes. The network controller 110 might also use a wired data connection (e.g., RS-232 (Electronic Industries Alliance/EIA), Ethernet (e.g., IEEE 802.3-2005, LAN/MAN CSMA/CD Access Method), power line communication (e.g., X10, IEEE P1675), USB (e.g., Universal Serial Bus 2.0 Specification), digital subscriber line (DSL), cable modem, T1 connection), etc., to enable access to additional off-platform resources.

In the illustrated example, the network controller 110 obtains output signals 118 from the PR arrays 102, and provides the output signals 118 to the processor 104 for filtering and/or further analysis. The processor 104 may execute logic that receives the output signals 118, identifies one or more orders of activation and one or more time differences based on the output signals 118, retrieves one or more distances between virtual beam edges from a memory location, and outputs gait velocity and levels of activity determinations 120. In addition, the other controllers 112 could provide support for user interface devices such as a display, keypad, mouse, etc. in order to allow a user to interact with and perceive information from the system 110. Thus, the gait velocity and levels of activity determinations 120 and other information could also be output via the other controllers 112. Additionally, portions or all of the gait velocity and levels of activity determinations 120 could be made locally at the PR arrays 102 or at another intermediate component such as an aggregator.

Thus, techniques described herein can provide for an array assembly that is a single unit, does not require complex mounting or careful measurement, and produces sensed areas that are uniform, reducing inaccuracy in measurements. Moreover, the sensed area can be treated with a tightly controlled beam that can be aimed precisely to avoid areas and doors that are not of interest. In addition, individuals may approach the edges of the virtual beams at approximately right angles, which can further improve sensing accuracy. As a result, the techniques are particularly useful in household settings to assess the falls risk of individuals such as the elderly.

Embodiments of the present invention are applicable for use with all types of semiconductor integrated circuit (“IC”) chips. Examples of these IC chips include but are not limited to processors, controllers, chipset components, programmable logic arrays (PLA), memory chips, network chips, and the like. In addition, in some of the drawings, signal conductor lines are represented with lines. Some may be thicker, to indicate more constituent signal paths, have a number label, to indicate a number of constituent signal paths, and/or have arrows at one or more ends, to indicate primary information flow direction. This, however, should not be construed in a limiting manner. Rather, such added detail may be used in connection with one or more exemplary embodiments to facilitate easier understanding of a circuit. Any represented signal lines, whether or not having additional information, may actually comprise one or more signals that may travel in multiple directions and may be implemented with any suitable type of signal scheme, e.g., digital or analog lines implemented with differential pairs, optical fiber lines, and/or single-ended lines.

Example sizes/models/values/ranges may have been given, although embodiments of the present invention are not limited to the same. As manufacturing techniques (e.g., photolithography) mature over time, it is expected that devices of smaller size could be manufactured. In addition, well known power/ground connections to IC chips and other components may or may not be shown within the figures, for simplicity of illustration and discussion, and so as not to obscure certain aspects of the embodiments of the invention. Further, arrangements may be shown in block diagram form in order to avoid obscuring embodiments of the invention, and also in view of the fact that specifics with respect to implementation of such block diagram arrangements are highly dependent upon the platform within which the embodiment is to be implemented, i.e., such specifics should be well within purview of one skilled in the art. Where specific details (e.g., circuits) are set forth in order to describe example embodiments of the invention, it should be apparent to one skilled in the art that embodiments of the invention can be practiced without, or with variation of, these specific details. The description is thus to be regarded as illustrative instead of limiting.

The term “coupled” may be used herein to refer to any type of relationship, direct or indirect, between the components in question, and may apply to electrical, mechanical, fluid, optical, electromagnetic, electromechanical or other connections. In addition, the terms “first”, “second”, etc. might be used herein only to facilitate discussion, and carry no particular temporal or chronological significance unless otherwise indicated.

Those skilled in the art will appreciate from the foregoing description that the broad techniques of the embodiments of the present invention can be implemented in a variety of forms. Therefore, while the embodiments of this invention have been described in connection with particular examples thereof, the true scope of the embodiments of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, specification, and following claims. 

1. A method comprising: partitioning an area into a plurality of zones using a plurality of virtual beams, the plurality of virtual beams being defined by edges of lateral fields of view of a plurality of passive motion sensors; and determining a gait velocity of a subject based on the subject's movement through the plurality of zones as measured by signals from the plurality of passive motion sensors.
 2. The method of claim 1, further comprising determining a level of activity of the subject in one of the plurality of zones based on a time spent by the subject in the zone as measured by signals from the plurality of passive motion sensors.
 3. The method of claim 1, wherein determining the gait velocity of the subject comprises obtaining a time of entry into and a time of exit from one of the plurality of zones of the subject based on an edge transition of a signal from the plurality of passive motion sensors.
 4. The method of claim 1, wherein the passive motion sensors comprise passive infrared sensors.
 5. The method of claim 1, further comprising retrieving one or more distances between virtual beam edges from a memory location.
 6. The method of claim 1, wherein the plurality of passive motion sensors comprises a first passive motion sensor and a second passive motion sensor disposed substantially parallel to the first passive motion sensor.
 7. The method of claim 1, wherein the plurality of passive motion sensors is disposed such that an expected motion to be detected is in a direction substantially perpendicular to the virtual beams.
 8. An apparatus comprising: a plurality of passive motion sensors, each of the passive motion sensors having a lateral field of view with an edge, the edges defining a plurality of virtual beams that partition an area into a plurality of zones, wherein output signals from the passive motion sensors indicate one or more of an order of activation of the passive motion sensors, a time difference between activation of the passive motion sensors, and a distance between virtual beam edges.
 9. The apparatus of claim 8, wherein the plurality of passive motion sensors comprises two passive motion sensors disposed horizontal to one another and define a two-dimensional vertical beam such that, if the two passive motion sensors are mounted to a wall of a hallway, the two-dimensional vertical beam is substantially perpendicular to a longitudinal axis of the hallway.
 10. The apparatus of claim 8, further including one or more leveling indicators.
 11. The apparatus of claim 8, wherein the plurality of passive motion sensors is disposed such that an expected motion to be detected is in a direction substantially perpendicular to the virtual beams.
 12. The apparatus of claim 8, wherein the plurality of passive motion sensors comprises a first passive motion sensor and a second passive motion sensor disposed substantially parallel to the first passive motion sensor.
 13. A system comprising: a plurality of passive motion sensors, wherein each of the passive motion sensors has a lateral field of view with an edge, the edges defining a plurality of virtual beams that partition an area into a plurality of zones; and a processor, in communication with a memory, configured to: receive signals from the plurality of passive motion sensors, and determine a gait velocity of a subject based on the subject's movement through the plurality of zones as measured by signals from the plurality of passive motion sensors.
 14. The system of claim 13 wherein output signals from the passive motion sensors indicate one or more of an order of activation of the passive motion sensors, a time difference between activation of the passive motion sensors, and a distance between virtual beam edges.
 15. The system of claim 13, wherein the processor is further configured to determine a level of activity of the subject in one of the plurality of zones based on a time spent by the subject in the zone as measured by signals from the plurality of passive motion sensors.
 16. The system of claim 13, wherein determining the gait velocity of the subject comprises obtaining a time of entry into and a time of exit from one of the plurality of zones of the subject based on an edge transition of a signal from the plurality of passive motion sensors.
 17. The system of claim 13, wherein the memory is configured to store one or more distances between virtual beam edges.
 18. The system of claim 13, further comprising a leveling indicator.
 19. The system of claim 13, wherein the plurality of passive motion sensors comprises two passive motion sensors disposed horizontal to one another and define a two-dimensional vertical beam such that, if the two passive motion sensors are mounted to a wall of a hallway, the two-dimensional vertical beam is substantially perpendicular to a longitudinal axis of the hallway.
 20. The system of claim 13, wherein the passive motion sensors comprise passive infrared sensors. 